Recent discoveries and increasing production of shale gas represent a significant new source of natural gas (essentially methane) lasting well into the 21st century. The technology to produce shale gas from shale formations in various places generally utilize the procedure of hydrofracking by injecting large amounts of water under pressure containing potentially harmful chemicals that represent significant safety and environmental dangers and harm. Moreover, substantial quantity of water resources is required to effectively implement the procedure. There is a public outcry against the use of such a technology. Thus, various alternatives have been suggested.
US patent application publication 2013/0056205 discloses the use of argon as a supercritical fluid and proppant for fracking, but this involves use of a gel, foaming agent or other gas for successful delivery to the subterraneum formation.
US patent application publication 2012/0118566 suggests pumping metacritical phase natural gas to create or extend one or more fissures in a subterraneum formation for fracking. This is disclosed as being an improvement over hydraulic fracturing methods that use water, liquid nitrogen or liquid carbon dioxide, the latter of which is disclosed as requiring foaming agents. Furthermore, the used carbon dioxide would be released to the atmosphere where it can contribute to global warming or other harmful environmental conditions.
Rather than injecting water or liquids with added chemicals to release natural gas in the earth by fracturing the shale rocks an environmentally friendly procedure of “dry fracking” with pressurized carbon dioxide is now discovered. The underground shale rock formations are effectively cracked open by the pressurized gas. The advantage of “dry fracking” with compressed CO2 is that the fracture pattern of the shale rock is more three dimensional, releasing more shale gas. The compressed CO2 is many times less viscous than water. Furthermore, some of the used CO2 for fracking is sequestered underground under pressure rendering the remaining shale more stable. As no water is used in dry fracking the environmental harm caused by hydrocracking is eliminated.
US patent application publication 2007/0261844 discloses a closed loop system for the capture and sequestering of carbon dioxide associated with the extraction of energy sources from large land masses. It suggests sequestering carbon dioxide in a shale reservoir or other formation. Sequestering of carbon dioxide, however, is not a viable solution for preventing the emission of carbon dioxide into the atmosphere, since the sequestration does not assure that the carbon dioxide will be maintained in the ground. The same is true of other forms of sequestration such as under the sea or in underground caverns.
CO2 injection into depleting oil fields and gas wells is used to improve secondary oil and gas recovery. The use of CO2 gas for fracking shale has not been utilized commercially and has been explored on a limited scale only. This technology was considered economically and technically impractical (see, e.g., K. Bullis, MIT Technology Review, Mar. 28, 2013).
In addition to using environmentally benign new fracking methods, there also is the need to convert shale gas to a convenient liquid fuel and chemical source material. The present invention avoids hydraulic fracking, as well as emitting carbon dioxide into the atmosphere while producing methanol providing an alternative general transportation fuel and chemical source material. It is thus a highly valuable process for replacing petroleum oil.